Description: This species is a member of the Polypodium vulgare complex, and has an interesting origin; it is an ancient hybrid between Polypodium vulgare sensu stricto and Polypodium cambricum. The species is a hexaploid with six sets of chromosomes; each set has 37 chromosomes, giving a total of 222 altogether. Because it is a hybrid it is intermediate in both form and habitat, with some plants being easily mistaken for either of the two parent species. Examination of the sporangia under a microscope is usually required for accurate identification.

All names: Polypodium interjectum Shivas; Polypodium vulgare ssp. prionodes (Asch.) Rothm.

Distribution Map from NBN: Polypodium interjectum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Polypodium interjectum at iNaturalist World Species Observations database.